Conventionally, as an apparatus for following an object to be imaged, a picture processing apparatus was proposed for following a targeted portion of a picture, by detecting the brightest region in an image picked up, on the basis of which the desired target portion is followed.
If any desired portion of an image can be tracked in such a way, then automatic focusing, iris adjustment and the like can be performed for this portion of the image to be able to achieve the improvement of the easy use of imaging devices.
However, there is a problem that the apparatus in which a desired portion of an image is tracked based on the brightest region in the image, can not follow a target portion of the image reliably, thereby being insufficient to use practically.
One method for solving this problem is to follow the target portion of an image on the basis of a picture characteristic thereof. However, this method has a disadvantage that a generally complicated structure is required for the apparatus.
A further method for solving this problem is to detect motion of a target portion of an image, by detecting a power of difference data obtained from a difference between frames, but in some cases, a detected result which is different from the motion of the target portion of an image may be obtained.
Another proposed method is to detect motion of a target portion of a picture, by using a time spatial filter apparatus. However, in this method, an amount of operation is large, therefore, this method has a disadvantage that a generally complicated structure is required for the apparatus.
On the other hand, conventionally, a method for transmitting a motion picture with high efficiency is proposed.
More specifically, in such a picture conversion apparatus, picture data sequentially inputted are divided into predetermined unit blocks, and then a motion vector is detected for every block, by using the block matching method.
Then, residual data is generated by subtracting picture data sequentially motion compensated for each block of picture data, after motion compensating picture data which is for one frame, on the basis of said detected result.
Thus, the amount of picture data is previously reduced, as compared to a case in which picture data is directly transmitted by using correlation between frames of motion picture.
This residual data is sequentially processed with discrete cosine transform and variable length coding, and is stored into a buffer memory after re-quantizing said residual data.
Thus, the picture data stored in the buffer memory are sequentially outputted from it at predetermined timing, and picture data is outputted keeping the amount of data at a constant value by changing a quantization step size of the re-quantizer, corresponding to a residual quantity of said buffer memory.
Thus, the motion picture can be transmitted with high efficiency, by using correlation of between frames of a motion picture.
Now, in the motion picture, a part of large motion has a characteristic that deterioration of picture quality is imperceptible.
Further, in such a motion picture, having a case where part of a picture has pronounced changes as compared with changes of thus around picture, another case of changes to the whole of a picture occurs.
In this case of a motion picture, it has a characteristic that deterioration of picture quality is more imperceptible, comparing to a case where the whole of a picture has constant motion.
With effectively using this unique characteristic, it is expected that more efficient transmission of motion pictures can be achieved. It is also expected that the quality of motion picture can be improved compared to the conventional technology.